The Potential of Production Forests for Sustaining Lichen Diversity: A Perspective on Sustainable Forest Management

Piret Lõhmus,Asko Lõhmus

doi:10.3390/f10121063

Abstract

There is a critical gap in our knowledge about sustainable forest management in order to maintain biodiversity with respect to allocating conservation efforts between production forests and set-asides. Field studies on this question are notably scarce on species-rich, poorly detectable taxon groups. On the basis of forest lichen surveys in Estonia, we assessed the following: (i) how much production stands contribute to maintaining the full species pool and (ii) how forest habitat conditions affect this contribution for habitat specialist species. The field material was collected in a “semi-natural forestry” system, which mitigates negative environmental impacts of even-aged forestry and forestry drainage by frequently using natural regeneration, tree retention, and low intensity of thinnings. We performed standard-effort surveys of full assemblages of lichens and allied fungi (such as non-lichenized calicioid and lichenicolous fungi) and measured stand structure in 127 2 ha plots, in mainland Estonia. The plots represented four management stages (old growth, mature preharvest forests, clear-cut sites with retention trees, and clear-cut sites without retention trees). The 369 recorded species represent an estimated 70% of the full species pool studied. Our main finding was that production forests supported over 80% of recorded species, but only one-third appears tolerant of management intensification. The landscape-scale potential of production forests through biodiversity-friendly silviculture is approximately twice as high as the number of tolerant species and, additionally, many very rare species depend on setting aside their scattered localities. The potential is much smaller at the scale of individual stands. The scale effect emerges because multiple stands contribute different sets of sensitive and infrequent species. When the full potential of production forests is realized, the role of reserves is to protect specific old-growth dependent taxa (15% to 20% of the species pool). Our study highlights that production forests form a heterogeneous and dynamic target for addressing the biodiversity conservation principle of sustainable forest management.

Highlights

Sustainable forest management (SFM) is a central politically-accepted concept that links forestry with broader issues of land use in the framework of sustainable development [1]
We provide a categorization of the species pool by management sensitivity, combining historical classifications [37,40] with a general approach to distinguish species whose viability in production forestry depends on the techniques used (e.g., [53]), and resolving the joint issue of poor data on extremely rare species
For SFM, we interpret such biodiversity variation related to species sensitivity as the “potential” of production forests to achieve biodiversity conservation goals through management

Summary

Introduction

Sustainable forest management (SFM) is a central politically-accepted concept that links forestry with broader issues of land use in the framework of sustainable development [1]. A critical gap in knowledge about maintaining forest biodiversity along with other forest use is how to allocate conservation efforts between production forests and set-asides of different type and size [6,7,8]. This gap remains partly rooted in incomplete knowledge on most forest organisms and their responses to management practices [9], which weakens conservation arguments in stakeholder processes and, makes these dependent on approaches to the precautionary principle [10]. A promising approach is to define a set of well-studied “focal” taxa with different habitat requirements for forest landscapes [11], its effectiveness to protect full biodiversity still has to be demonstrated [12]

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Discussion

Conclusion